What does blockage of heart arteries, or coronary artery disease mean?

The heart is a strong pump that delivers fresh oxygenated blood to different organs in the body with each heartbeat. The heart muscle itself gets blood through arteries called coronary arteries. These conduits called coronary arteries run on the surface of the heart. The disease of these arteries is called coronary artery disease.

Note the heart arteries (coronaries) running on the surface of the heart.

Picture from Cleveland Clinic Website

 The blockage of these arteries can cause lack of blood supply to the heart muscle. The most dreaded consequence of the blockage is heart attack, which can be a fatal event. The blockages can also lead to heart failure, chest pain etc.

How can I find out if my heart arteries are blocked?

Coronary artery disease, technically speaking, means any disease of these arteries. The tests done in everyday cardiology practice mostly check for the blockage in the heart arteries that are bad enough to cause decreased blood supply to the heart muscles.

There are two kinds of tests for the diagnosis of coronary artery disease. One group includes different kinds of stress tests and the other one includes tests that actually look at the anatomy of heart arteries. The later group includes coronary angiogram, also known as heart cath (short for catheterization) and CT angiogram.

The way to understand the difference between these two modalities is the following. Let us say you want to see if the sprinkler system for the grass in your backyard is working well. There are two ways to do that. You can look at the grass in the back yard. If the grass on the northwest corner of the yard appears unhealthy, the sprinkler system to that area may not be working well. The other possibility is to actually run an instrument through the sprinkler pipes to see if there are blockages. The stress test involves looking at the ‘grass’ (heart muscle) and coronary angiogram involves looking through the ‘pipes’ (heart arteries).

Which is better at diagnosing coronary artery disease- stress tests or coronary angiogram?

It really depends on the situation. A heart cath, although a very safe test, is an invasive procedure. A non-invasive test like a stress test is usually preferable screening test. However, there are several scenarios where a heart cath is considered first choice for the diagnosis of coronary artery disease.

Isn’t coronary angiogram a gold standard?

The coronary angiogram gives us an anatomical description of coronary arteries. The anatomy, unlike biochemistry or physiology lends itself to concrete mental grasp. It is also likely to be interpreted in a somewhat similar fashion by different observers.

 

                                        

Notice the tight spot marked by an arrow. The extent of narrowing is estimated based on the appearance of adjacent area.

Picture from texasheart.org

 The coronary angiogram has some shortcomings including:

-         The coronary angiogram is a two dimensional picture. The inner lumen of the artery may be significantly diseased without showing obvious abnormalities on the two dimensional pictures.

-         Comparing a diseased segment to the adjacent ‘normal’ segment makes the diagnosis of disease or blockage. If whole length of the artery is diseased, the artery may be uniformly narrowed throughout its length, and hence give the impression of a normal artery.

-         The angiogram looks at the anatomical characteristics of the vessels. While looking at angiographic findings, we run the risk of presuming that coronaries are just like water pipes. In fact, coronaries are living structures that have their own dynamic behavior unlike dead water pipes.

 If coronary angiogram has all these shortcomings and is invasive, why do it?

Coronary angiogram continues to be a very important test for the diagnosis of blockages of heart arteries. Two of the important ways to deal with coronary artery disease are bypass surgery and angioplasty/stent placement. An angiogram is an indispensable step before either of these two treatment options.

If I have a normal stress test today, does that mean that I can rest assured that I will not have a heart attack in the next 5, 10 or 15 years?

Unfortunately, a normal angiogram or a stress test today does not guarantee against a heart attack tomorrow. We have known this ever since we learned about the phenomenon of plaque rupture.

A picture of plaque rupture which leads to something like a numerous blood-cells-pile-up leading to a heart attack

Slide from escardio.org

Not too long ago, we used to think that coronary artery blockage progressed in a linear fashion. This meant 60% blockage will turn into 70, then 80 and eventually 100%. The studies have now shown that close to 70% of heart attacks occur in the arteries that were less than 50% blocked at the time of heart attack. Fifty percent is the severity that can be easily missed on a stress test or even on coronary angiogram. I am not saying this to propagate a defeatist attitude, but to make a stronger case for proactive approach toward management of coronary artery disease. An important part of proactive approach is management of risk factors

What is the importance of tests for diagnosis of coronary artery disease?

Various diagnostic tests help with timely detection of coronary artery disease. This can prevent many potentially fatal events. A diagnostic test is very important if there are signs and symptoms of disease of heart arteries or if suspicion for blockages in heart arteries is high. As an example, diabetics may have severe blockages in the heart arteries despite the absence of classical symptoms.

The information above is based on actual questions that I have been asked. I hope this gives you a good perspective on coronary artery disease. Various tests for the diagnosis remain an important part of management of heart disease.

What are different types of tests used to diagnose coronary artery disease or blockage of heart arteries?

There are two kinds of tests:

Stress tests:

- Exercise treadmill test or stress test

- Exercise nuclear scan or nuclear stress test or Cardiolyte stress test

- Exercise stress echo or echocardiogram

- Adenosine nuclear stress test

- Dobutamine nuclear stress test

- Dobutamine stress echo

The last three are also called as chemical stress tests.

Tests looking at the anatomy of coronary arteries:

Coronary angiogram or heart catheterization

CT angiogram

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